Fig. 2
Comparative decline in lung function metrics by smoking status. This represents the longitudinal change in lung function according to smoking status. The changes in lung function during the study period were estimated using a linear mixed regression model based on baseline lung function and expressed as a percentage decline. Data was adjusted for age, sex, height, and baseline lung function. (A) FEV1. (B) FVC. (C) FEV1/FVC ratio. (D) DLCO. The blue line represents the never-smoker group, the green line represents the ex-smoker group, and the red line represents the current smoker group